Such an antenna is intended to detect and to locate underwater sources of acoustic noise, for example. To obtain good performance both in detection and in location, it is necessary to work over a spectrum of low or medium frequencies and to have an antenna the gain of which is high in order to obtain a satisfactory signal to noise ratio (in numerous applications a gain of 20 dB is necessary). By medium frequencies is meant frequencies lower than 12 kHz.
At present, acoustic antennas for receiving underwater waves include acoustic sensors that will be referred to as acoustic panels in the remainder of the text. These acoustic sensors include at least one acoustic pick-up enclosed in a flexible material coating. The assembly thus constituted forms an acoustic panel referred to as an acoustic panel. An acoustic panel has a globally rectangular shape.
The acoustic panels are mounted on a support, for example on the hull of a submarine. The acoustic panels have a degree of freedom in bending so as to be able to mate with the shape of this hull.
The panels are held against the wall by clamping them by means of two flanges attached along the longer sides of the acoustic panels. The acoustic panels are sandwiched between the flanges and the hull of the submarine. The ends of the flanges are mounted on rails on either side of the panels extending longitudinally in the direction of the width of the panels.
The flanges have a curved shape approximating the curvature of the submarine, which enables them to clamp the acoustic panels against the hull of the submarine.
Now, at present, rigid metal flanges are used. They provide effective clamping of the acoustic panels only on a hull having a predetermined curvature.
This clamping solution has a certain number of disadvantages. Because of manufacturing tolerances in respect of the hull of a submarine and also the flanges, it can happen that the clamping of the acoustic panels is not efficacious. If the curvature of the hull is less than foreseen (radius of curvature greater than foreseen) or if the curvature of the flanges is greater than foreseen (radius of curvature less than foreseen), the acoustic panels are not correctly clamped against the hull of the submarine. Knowing also that the acoustic panels may be deformed because of hydrodynamic disturbances, there is therefore a risk of the panels escaping from their fixing flanges.
On the other hand, if the curvature of the hull is greater than foreseen (radius of curvature less than foreseen) or if the curvature of the flanges is less than foreseen (radius of curvature greater than foreseen), the acoustic panels clamp the panels too firmly, which leads to premature wear of the panels.
Moreover, it is necessary to provide different flanges for different submarines the hulls of which have different radii of curvature or for a single submarine the hull of which has a varying radius of curvature.